Cassandra Clare said this quote

Why can't I go to Idris with you, then?Because it's not safe for you thereO and it's safe for me here? I've been nearly killed almost a dozen times in the past month.That's because Valentine has been concentrating on the two Mortal Instruments that were here. He's going to shift his focus to Idris now. We all know it--We're hardly as certain of anything as all that. And the Clave wants to meet Clarissa. You know that, Jace.The Clave can screw itself.